AFAIU, import duties aren't really something you're necessarily "charged" as much as it's something you have a legal obligation to pay. Sure, maybe you could buy a car in Canada and bring it in to the US without paying the tariffs... we call that smuggling.
It's hardly smuggling if there is no process to collect the duties from you. Are you meant to walk into a random local government office and hand them a bunch of cash and say "i think i owe you this" ?!
What if it's a used car, not new, what's the tariff then?
I can't believe there is no process to collect it if you import it just by driving across the border.